The present invention relates to a grease composition for construction equipment.
A grease to which a black solid lubricant such as molybdenum disulfide or graphite is added has conventionally been applied to parts of construction equipment to be lubricated because of the excellent lubricity thereof. However, such a grease suffers from various problems in that, when the grease is used as a lubricating grease for construction equipment which have recently been provided with beautiful multi-color coating, the grease considerably impairs the appearance of the equipment and the body and/or clothes of operators of the equipment are contaminated with the grease since the grease is black in appearance. To solve these problems, many attempts have been done, which make use of extreme-pressure agents having a color other than black such as organic molybdenum compounds, polytetrafluoroethylene ( PTFE ), an adduct of melamine with cyanuric acid (MCA), or the like. The use of a lubricant having a color other than black permits the solution of the problem concerning the appearance of construction equipment and pollution of the working environment, but there has never been developed any grease composition exhibiting the lubricity comparable to that of the molybdenum disulfide-containing grease conventionally used. In addition, Japanese Un-Examined Patent Publication (hereinafter referred to as "J. P. KOKAI") No. Hei 7-82583 discloses a grease composition which makes use of synthetic mica as a lubricity-improving agent, but the composition exhibits poor lubricity and would not have quality sufficient for use as the grease composition for construction equipment.
Moreover, J. P. KOKAI No. Hei 7-41781 discloses a lubricant composition comprising phosphate glass. The lubricant composition is excellent in resistant to load as compared with the conventional lubricant compositions. However, the lubricant composition is still insufficient in the resistant to load when it is applied to construction equipment which require extremely high resistance to load.